Ophthalmology of clinically normal alpacas (Vicugna pacos) in the United Kingdom: a cross-sectional study

BACKGROUND: Alpacas are being more frequently presented to veterinarians in the UK. It is important to validate whether published normal ocular parameters are consistent with the alpaca population in the UK. METHODS: Ophthalmic examinations were performed on healthy alpacas (Vicugna pacos) from three farms in East Anglia, UK. RESULTS: On direct ophthalmoscopy of 35 alpacas, there was a 50 per cent prevalence of opacities within the lens in alpacas older than two years old (n=8/16). There was a 36.8 per cent prevalence of persistent hyaloid arteries in alpacas under two years old (n=7/19). The mean Schirmer tear test-1 value was 20.0 ±6 mm/minute (n=40). The mean intraocular pressure measured by rebound tonometry was 17.2 ±5.5 mmHg (n=46), and applanation tonometry resulted in statistically similar values (P=0.30; n=25). There was a significant variation in intraocular pressure throughout a 24-hour period (n=8). Fluorescein dye was not detected at the nostrils of any of the alpacas which underwent a Jones test to assess nasolacrimal duct patency (n=8). CONCLUSION: The ophthalmic findings appear largely consistent with previously published values from North America and continental Europe. Variations include the large range of measurements obtained and evidence of diurnal variation in intraocular pressure.